Interlocking stair form



N. BOIS.

INTERLOCKING STAIR FORM.

APPLICATION FILED 05c. 24, i9H.

1,304,533. Patented May 27, 1919.

INVENTOR.

A TTORNE Y N. BOIS. ENTERLOCKING SIAIB FORM. APPLICATION man 050. 24. I91].

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INVENTOR.

' ATTORNEY UNITED STATES PATENT oEEIoE.

NATHANIEL BOIS,' 61 SAN FRANCISCO, CALIFORNIA.

INTERLOGKING STAIR-FORM.

Specification of Letters Patent.

Patented May 27, 1919.

Application filed December 24, 1917. Serial No. 208,990.

interlocking. stair forms of the type disclosed in the United States Patent N 0. 1,244,021 issued to me on the 23rd day of October, 1917, and consists 1n the elimina- -tion of certain parts of the above referred to type without a corresponding omission of function; and the ob]ects of the present invention are:

. First, to provide an improved stair form of improved construction requiring less material;

Second, to provide an improved stair form wherein a simflplified construction produces a rigid and e cient form for the support of slabs or concrete filling; and

Third, to provide an improved sta1r form of the type described adapted to provide a form for concrete stairs wherein the nosing of said concrete may extend above the metal nosing of the form.

I accomplish these several features by means of the device disclosed in the drawings forming a part of the present specification wherein like characters of reference are used to designate similar parts throughout the said specification and drawings, and in which Figure 1 is a perspective view' partly in section disclosing the improved-stair form;

Fig. 2 is a vertical sectlon view on an enlarged scale of a portion of a stair-case disclosing the invention more in detail;

Fig. 3 is a broken front elevation of Fig.

2; and

Fig. 4 is a vertical sectional view of a modified form of tread. Referrin to the drawings the numeral 1 is used to designate in general a stair form consisting of a riser 2 and a tread 3.

The tread 3 is provided with an upwardly extending flange or nosing 4 the purpose of which w ll hereinafter be more fully described. The riser 2 is provided at the upper end thereof with a rearwardly .facing channel comprising a bottom wall 6 a forward side wall 7, and a downwardly and rearwardly inclined top wall 8.-

In assembling the stair forms the upwardly extending nosin 4 of one tread istom surface of the tread 3 on one stair form resting on and in continuous contact with the top of the bottom wall 6 of the channel on the riser 2.

The ends of the riser'2 and tread3 are inserted into a form so as to become embedded within concrete stringers 12 formed on each side of the stair forms 1, said strin ers 1'2 bemg provided with the usual rein orcing rods 14 to which the stair forms are tied by means of twistedwire eyelets 16 as disclosed in Figs. 1 and 3 .of the drawings.

After a suflicient number of stair forms have been interlocked to form a stairway, concrete treads 9, of greater depth than the height of the nosing 4, are formed upon the v trends 3 so as to provide'a concrete nosing 10 above the metal channel interlocking the nosing 4. Owing to the rearward and downward inclination of the top wall 8 of the channel formed on each riser 2 the concrete nosing 10 diminishes in sectional area toward the forward end of the stair. thereby providlng a concrete nosin-g strength and one not likely to crack or break ofi through usage.

The concrete nosing 10 extendin above and channel of t e stair which may be poured concrete to securely retain the interlocked nosing and channel as disclosed in Fig. 4 of the drawings.

'It is obvious from the 'foregoin that I have provided an improved and slmplified construction for interlocking stair forms 10 of superior wherein a saving of weight and material 13 effected without diminishing the eihciency of the interlocked forms. 7

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. The combination with a stair form having a tread, a riser connected thereto, and a rearwardly facing channel formed on the upper edge, said channel comprising a bottom wall, a downwardl inclined top wall, and a forward side we 1, of a second stair form having tending nosing extendin into the channel and between the side wal and inclined top wall on the riser to interlock said riser and nosin r 2. 'he combination with a stair form having a tread, a riser connected thereto, and a rearwardly facing channel formed on the upper edge of said rise'r, said channel comprising a bottom wall, a downwardly inclined top wall and a forward side wall, of a second stair form having a tread and an upwardly extending nosing formed on the 1 forward edge of said tread and extending a tread and an upwardly exinto the channel onthe riser and in contact. with the bottom wall thereof and the upwardly extending nosing of the tread is held in contact wlth the forward wall of the channel on the riser by the inclined top wall of said channel to interlock said riser and tread.

3. The combination with a stair form having a tread and riser and nosing formed on the front edge of said tread, of a second stair form having a similar tread, a riser connected thereto, and a rearwardl facing channel formed on the top of the riser, said riser comprising a bottom wall, a forward side wall and a top rearwardly and downwardly inclined top wall, said channel engaglng the bottom of the forward edge of the tread and the forward wall and inclined top wall engaging the upwardly extending nosing on the tread to interlock said nosing and user.

In witness whereof I hereunto set my signature. 7

NATHANIEL BOIS. 

